Physicochemical studies of differences between normal and tumor-promoting cells include: 1) The evaluation of morphological differences, by electron microscopy, between normal hepatocytes and those which are transformed through exposure to chemical carcinogens in vitro. 2) The comparison of kinetic and electrophoretic behavior of lactate dehydrogenase (LDH) isoenzymes in normal and chemically transformed hepatocytes in relation to the increased excretion of acid observed following transformation in vitro. 3) The refinement in methods for a) the chromatographic separation of LDH isoenzymes and b) the computer analysis of the kinetic data. 4) The application of these methods to the purification and analysis of LDH-1 from red blood cells of a human subject for genetic diagnosis (in collaboration with M. Freeman). 5) The NMR analysis of the structure of cyclocytidine in order to understand its effect upon DNA damage and repair in normal and xeroderma pigmentosum human fibroblasts (in collaboration with R. Setlow).